Project Summary/Abstract The cerebellum (Cb) controls fine motor control, motor learning, body spatial awareness, and cognitive functions. The structure of the Cb is complex and partitioned at multiple interdependent levels including shape, gene expression and circuitry. Localized defects in the shape of the Cb disrupt afferent circuitry and are associated with many diseases such as Jouberts syndrome and Dandy-Walker. The engrailed homeobox transcription factors EN1 and EN2 (EN1/2) regulate many aspects of Cb development including foliation. EN1 and EN2 are implicated in Parkinsons disease while EN2 is a susceptibility locus for Autism spectrum disorders. The aim of this project is to determine the roles of EN1/2 in regulating the dynamic behavior of granule neuron progenitors (GNPs) within the external granule layer (EGL) that contribute to foliation. First, slice culture, live imaging and cell tracking will be used to measure the dynamic movements of GNPs in the EGL and compare them between long and short folia, as well as the base of the fissures, known as anchoring centers, which restrict cells from crossing between folia. This analysis will focus on the dynamics of GNP dispersion, as well as changes in cell shape, formation of protrusions and rate of cell division versus differentiation. The results should uncover behaviors that are specific to particular folia and that regulate the allocation of the correct number of GNPs to each folium and thus, the size and shape of folia. Second, slice culture, live imaging and tracking of scattered cells ablated for En1/2 (mosaic mutants) will reveal cell autonomous regulation of particular aspects of GNP dynamics regulated by EN1/2 that are important for foliation. Third, laser capture microdissection and microarray analysis will be used to identify genes expressed specifically in GNPs in anchoring centers at the base of fissures, while the localization of structural proteins in anchoring centers will be mapped with fluorescent immunohistochemistry in cleared cerebella. This project will provide a unique training opportunity and further the understanding of Cb foliation which is necessary for proper circuitry and function. !